Hi,
Seems like you mixed the concepts of Grafanas internal database storage (that can be postgres) and the postgres data source which you can use to visualize data in Grafana.
In hosted grafana there’s already an internal database that you cannot change and you don’t need to care about any database schema.
So I’m guessing that you’re referring to configure a postgres data source to be used for visualizing data? Here you basically can have whatever schema as long as you can write a query that would return at least a timestamp and some numeric value.
If you want to use hosted grafana with a postgres DB in AWS RDS I’m guessing that the following post is interesting for you: MySQL datasource validation IP address range
For reference, see Using PostgreSQL in Grafana documentation
Good luck
Marcus